Titanium oxide has a high refractive index and excellent covering power, coloring ability, and ultraviolet protection ability. Thus it has traditionally been widely used as a pigment in products such as paint, plastics, and cosmetics. Titanium oxide contained in bases for these products as an ultraviolet protective agent is commonly fine particle powder having a mean primary particle size of 0.1 μm or less, which is a result of the pursuit of ultraviolet protection ability and transparency. Examples of known processes for producing titanium oxide include a method of thermally hydrolyzing titanyl sulfate or titanium tetrachloride in the aqueous phase and a method of neutralizing and hydrolyzing such a compound (see Patent Document 1, for example).
However, because of its very small particle size, such fine particle powder has high oil absorption and easily aggregates: thus it is difficult to disperse such powder in a product base. In addition, products such as cosmetics containing the fine particle powder provide a high ultraviolet protective effect in the UV-B region (280 to 320 nm) while they have problems such as poor transparency in the visible region (400 to 700 nm) and roughness and poor spreadability in actual use.
Patent Document 2 discloses that a porous titanium oxide powder can be obtained by thermally hydrolyzing a titanium salt solution in the presence of an aliphatic alcohol and then further heat treating the solution with an acid.
This porous titanium oxide has an excellent ultraviolet protective effect, usability, and transparency in the visible region, but it is desirable to further improve these properties.    Patent Document 1: Japanese Unexamined Patent Publication No. 55-10428    Patent Document 2: Japanese Unexamined Patent Publication No. 2004-292266